Drive device with brake incorporated for an electrically operated vehicle

ABSTRACT

A drive device for an electrically operated vehicle, in particular a wheelchair, having at least one rim with rim well and actual shaft wherein a brake is located in a brake space defined in part by a gap between a pair of spaced part bearings on the axle shaft of the device.

This is a continuation, of application Ser. No. 08/875,014, filed Jul.16, 1997, now U.S. Pat. No. 5,920,136.

The invention relates to a drive device for an electrically operatedvehicle, in particular for a wheelchair, having at least one rim withrim well and an axle shaft.

There are very many forms and designs of electrically operated vehicles.These include, for example, electric automobiles, vehicles in theinternal area of train stations and industrial buildings, children'svehicles and in particular also wheelchairs. In most cases here thedrive wheels are connected via an axle shaft to a transmission, forwhich reason the power consumption of such drives is significantlyincreased.

In recent time a change has been made to integrating the drive and inparticular the motor into the wheel itself, so-called wheel-hub drivesor drum motors being known here. These include electronically commutatedwheel-hub motors. However, these wheel-hub motors are likewise connectedto the drive shaft via a transmission, so that considerable energy isstill lost.

The present invention is based on the object of providing a drive deviceof the above-mentioned type with which the vehicle can be operated in aslow-power and low-noise a manner as possible and has the lowest possibleconstructional width. Furthermore, the braking function is to besignificantly improved.

SUMMARY OF THE INVENTION

In order to achieve this object, an annular channel is formed betweenthe rim and the axle shaft, and a motor and a brake are integrated insaid annular channel.

The significant advantage of this drive device according to theinvention resides in the fact that the constructional width of theoverall drive is reduced to a minimum. The entire drive, and the brakingsystem as well, is arranged inside the rim itself. A chassis of avehicle or, for example, the chair of a wheelchair, is then connected tothe static part of this drive device in any desired manner.

The motor and the brake are preferably separated from each other by aninner housing ring. This inner housing ring is a part of the static partand presents itself for the connection to the chair or the chassis ofthe vehicle. Furthermore, the stator part of the motor is likewise to berotationally firmly connected to this inner housing ring. The rotorpart, on the other hand, is arranged on the rim itself, around thestator part. Toward the stator part, the rotor part is equipped withcorresponding magnetic strips, which form an air gap toward the statorpart. In this way, the rotor part rotates around the stator part.

Permanent magnetic strips, which ensure a high power transfer, arepreferably used.

As a result of the arrangement selected, it is possible to support theinner housing against the axle shaft via two bearings, these bearingsbeing spaced relatively far apart from each other in one exemplaryembodiment. This achieves a maximum bearing spacing for thecorresponding wheel with, at the same time, the minimum constructionalwidth of the overall drive. Furthermore, it is possible to use bearingdesigns which can readily be adjusted without play. Rolling bearings(shouldered radial-thrust bearings), which ensure the greatest possiblequietness of running, are the most obvious.

A significant feature of the present invention is, however, directed tothe braking system. For wheelchairs in particular it is necessary thatif the electrical system fails, there must be a stopping brake whichbrakes the wheelchair as quickly as possible. According to the presentinvention, this stopping brake is likewise integrated in the annularchannel of the rim, so that no additional space has to be occupied.

A brake space is formed by the inner housing ring together with a ringmade of a ferritic material, at least one brake disk projecting intosaid brake space. Preferably, however, a plurality of brake disks isused. These brake disks are seated along an axis of the axle shaftitself, but they can be displaced axially with respect to the axleshaft. This is ensured by a splined connection between brake disk andaxle shaft, the brake disk preferably being produced from a materialused for brake linings.

The brake disk is in turn assigned brake rings which can be displacedalong the axis of the axle shaft. These brake rings are preferablycoupled to the inner housing ring via splined connections. If aplurality of brake disks and a plurality of brake rings are used, thebrake rings are always between two brake disks. In order to brake thevehicle, the outermost brake ring is assigned a force store whichpresses the outermost brake ring against its adjacent brake disk. If thearrangement has a plurality of brake rings and brake disks, thispressure is forwarded from brake disk to brake ring and vice versa. Thisresults in effective braking of the vehicle.

By contrast, in order to cancel the braking effect, an axially actingmagnetic coil is assigned to the outermost brake ring. This magneticcoil acts counter to the force of the force store and attracts theoutermost brake ring, so that the brake disks can run freely between thebrake rings. In this arrangement, the magnetic coil is located in anannular space in the above-mentioned ferritic ring. If the power fails,then the magnetic coil releases the outermost brake ring, and immediatebraking takes place. If the brake is then to be released once more, thistakes place via the magnetic coil or, if the electrical system is stillout, via a device by means of which the outermost brake ring is movedaxially, for example by hand, counter to the force of the force store.This device may comprise any desired levers, eccentric levers or leverarrangements.

In the one exemplary embodiment, the brake disks and also the brakerings are otherwise located between the two above-mentioned bearings, sothat a very good force ratio during braking is ensured. Twisting as aresult of the braking action cannot occur.

In another exemplary embodiment, however, the brake disks and the brakerings are arranged outside the two bearings, these two bearings beingsupported on the one hand against the axle shaft and on the other handagainst an axle sleeve which is integrally molded on the inner housingring. It is thus possible, as required, to set up the overall drivedevice with a very low overall length or else with a relatively largeoverall length, which in turn has other advantages.

What is to be emphasized primarily is that when releasing the brake orelse when initiating the braking operation, hardly any noise isproduced. It is possible to hear only a slight click when the magneticcoil attracts the outermost brake ring. This constitutes a majoradvantage by comparison with the previously known braking devices.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages, features and details of the invention emerge fromthe following description of a preferred exemplary embodiment, and withreference to the drawing, in which

FIG. 1 shows a partial cross section through a drive device according tothe invention for an electrically operated vehicle;

FIG. 2 shows a partial cross section through a further exemplaryembodiment of a drive device according to the invention for anelectrically operated vehicle.

DETAILED DESCRIPTION

The present case concerns a so-called wheel-hub drive or drum motorwithout transmission. Formed in an axle shaft 1 at the end is a blindhole 2, into which a journal 3 of a rim 4 engages. The journal 3 isrotationally firmly fixed in the blind hole 2 of the axle shaft 1, forexample being shrunk in, bonded or the like.

The journal 3 projects approximately centrally out of a rim disk 5 whichis bounded at the edge by a rim well 6. The rim well 6 merges in onepiece into an inner rim flange 7, which is adjoined by a housing ring 8.From the outside at the transition from rim disk 5 to rim well 6, a rimflange ring 9 is placed in a removable manner on the rim 4, appropriatefastening elements being indicated with dash-dotted lines. Theremovability of the rim flange ring 9 ensures that, for example, even awheelchair user can easily remove a tire which is located in the rimwell 6 but not shown in more detail, and replace it with a new one.

Overall, the rim 4 together with the axle shaft 1 forms an annularchannel 10 for the accommodation of a motor 11 and of a stopping brake12. In this case, the motor 11 is designed as an electric motor. Itsrotor part 13 is rotationally firmly connected to the rim 4, thecorresponding rotor part 13, as a laminate stack, resting snugly in themanner of a circular ring against an inner face 14 of the rim well 6 andbeing supported on one side against a shoulder 15 which is molded intothe inner face 14.

From the other side, a pressure ring 16 presses on the rotor part 13 andpresses the latter against the shoulder 15, with the result that therotor part 13 is clamped between the shoulder 15 and the pressure ring16. The fixing or the clamping is carried out via fastening elements 17which are indicated with dash-dotted lines.

Magnetic strips 18, in particular permanent magnet strips, are placed onthe rotor part 13, parallel to a main axis A of the drive. Theindividual magnetic strips 18 are arranged spaced apart from one anotheralong the rotor part 13.

Between the magnetic strips 18 and a stator part 19, which is likewisedesigned as a laminate stack, there is an air gap 20. The stator part 19is, as its name suggests, fixed and is pushed on an inner housing ring21 and rotationally firmly connected to the latter. To this end, thisinner housing ring 21 likewise forms a shoulder 22, against which thestator part 19 stops. The stator part 19 is braced by a stepped washer23 which, at the other end of the shoulder 22, presses on the statorpart and is connected to the inner housing ring 21 via fasteningelements 24 indicated by dash-dotted lines. Clearance 25.1 toaccommodate the respective winding overhangs of the stator part 19 areindicated on either side of the stator part 19.

Since the pressure ring 16 can rotate together with the rim 4, but theinner housing ring 21 is designed to be fixed, there is located betweenthe two of them a seal 25 which is preferably composed of two plasticparts. In this case, one plastic part is likewise rotatable with respectto the other plastic part, but between the two plastic parts there is alabyrinth seal 26.

In order that the rim 4 can rotate with respect to the inner housingring 21, a bearing 28 and 29 is in each case provided between the innerhousing ring 21 and the axle shaft 1, and between a ferritic ring 27,which is connected to the inner housing ring 21, and the axle shaft 1. Arolling bearing (shouldered radial-thrust bearing) is most suitably usedhere. The two bearings 28 and 29 are braced by appropriate lateralstops, the overall fixing being performed via a nut 30 which is placedonto an external thread 31 of the axle shaft 1.

Together with the axle shaft 1 and the ferritic ring 27, the innerhousing ring 21 forms a brake space 32, into which three brake disks33.1, 33.2 and 33.3 project from the axle shaft 1. These brake disks 33can rotate freely in the brake space 32. They consist of an appropriatebrake-lining material and are rotationally firmly fitted to the axleshaft 1. To this end, the axle shaft 1 has appropriate female splines 34running parallel to the axis A, into which male splines of the brakedisks 33 (not shown in more detail) engage. In this way, the brake disks33 are pushed on the axle shaft 1 and can be moved along the axis A.Their movement is however limited by brake rings 35.1, 35.2, 35.3 and35.4. These brake rings 35 have female splines, likewise not shown inmore detail, into which male splines 36 engage, said splines projectingin turn into the brake space 32 from the inner housing ring 21. In thisarrangement, the outer brake ring 35.1 can in addition be connected tothe inner housing ring 21 via the fastening element 24. The other brakerings 35.2, 35.3 and 35.4 are, however, intended to be arranged suchthat they can be displaced along the axis A.

The desired braking action between the brake disks 33 and the brakerings 35 is produced via a force store 37 which, in the presentexemplary embodiment, is an appropriately dimensioned spring or springs.This force store 37 presses on the outermost brake ring 35.4, via whichthe following brake disks 33 and brake rings 35 are then pushedtogether. As a result of the arrangement of a plurality of brake disks33 and brake rings 35 one behind another, the diameter of the overallstopping brake 12 can be kept extremely small. The number of brake disks33 and brake rings 35 can be selected arbitrarily, depending on thebraking torque or holding moment required.

A further major advantage of the arrangement of a plurality of brakedisks and brake rings resides in the fact that the force of the forcestore 37 can be kept relatively small, as a result of which thedevelopment of noise during the actuation of the brake is also verysmall. The electrical losses are also extremely low as a result.

In order to open the stopping brake 12, an annular space, in which thereis a magnetic coil 38, is indicated in the ferritic ring 27. As long asthe overall drive is supplied with power, the magnetic coil attracts theoutermost brake ring 35.4 counter to the force of the force store 37, sothat there is no force connection between the brake disks 33 and thebrake rings 35. The brake is released.

However, if the power fails, then the magnetic coil in the annular space38 is also not supplied with power, so that the outermost brake ring35.4 is released and the brake rings and brake disks close under thepressure of the force store 37. In order that the outermost brake ring35 can interact with the magnetic coil, the outermost brake ring 35.4 islikewise composed of a ferritic material, for example of steel. Theremaining parts of the drive, with the possible exception of the axleshaft 1, may be composed of aluminum.

Precautions must be taken, however, that the stopping brake 12 can alsobe released when there is no power flow to the magnetic coil in theannular space 38. To this end, only one opening 39 through a cover 40and the ferritic ring 27 is indicated, through which a correspondinglever or any desired pulling element engages, with which the outermostbrake ring 35.4 can be guided by hand counter to the force store 37.However, the configuration of this lever is of subordinate importance.

The entire drive is fixed to an electric vehicle which is not shown inmore detail. To this end, a possible fastening 41 between the innerhousing ring 21 and the vehicle is merely indicated.

According to the exemplary embodiment in accordance with FIG. 2, an axleshaft 1.1 is connected to a rim 4.1 by means of countersunk screws 50.In this case a disk-shaped ring 51 of the axle shaft 1.1 rests on acorresponding inner rim well 52. The other rim well 6.1 likewise mergesin one piece into an inner rim flange 7.1, which is adjoined by ahousing ring 8.1. It is also possible to see here a rim flange ring 9.1which, however, also forms approximately one half of the rim well 6.1.By this means, the removal of a tire by a wheelchair user is once againfacilitated.

In the present exemplary embodiment, the housing ring 8.1 is designed tobe significantly lengthened with respect to that according to theexemplary embodiment of FIG. 1, so that an annular channel 10.1 for theaccommodation of a motor 11.1 and of a stopping brake 12.1 is notarranged underneath the rim well 6.1 but underneath or inside thehousing ring 8.1. A corresponding rotor part 13 of the motor 11.1 restson an inner face 14.1 of the housing ring 8.1 and is pressed against ashoulder 15.1 by an outer ring 53, by means of fastening elements 54which moreover pass through a slip ring 55.

An inner disk 56 engages over the entire motor region 11.1 in a sealingmanner, said inner disk 56 merging into the inner housing ring 21.1. Thestator part 19.1 is pushed onto this inner housing ring 21.1 and fixedbetween a stepped washer 23 and a shoulder 22.

Opposite the inner disk 56, an axle sleeve 57 projects from the innerhousing ring 21.1, the axle sleeve 57 partially surrounding the axleshaft 1.1 and being supported against this axle shaft 1 via the twobearings 28 and 29.

Whereas according to the exemplary embodiment in accordance with FIG. 1the stopping brake 12 is arranged within the two bearings 28 and 29, thestopping brake 12.1 according to the exemplary embodiment in accordancewith FIG. 2 is located outside the bearing 29. Otherwise, the stoppingbrake 12.1 is of identical design, for which reason further descriptionwill be dispensed with.

I claim:
 1. A drive device for an electrically operated vehiclecomprises an axle shaft disposed alone an axis A; at least one rimconnected to the axle shaft for rotation therewith, said at least onerim having a rim well wherein said rim well and said axle shaft definetherebetween an annular channel; an inner housing ring positioned insaid annular channel disposed along an axis B which is substantiallyparallel to axis A and axially dividing said annular channel into amotor space and a brake space, said inner housing ring being supportedon the axle shaft by a pair of bearings axially displaced on the axleshaft along axis A and defining therebetween in said brake space a gap;and a brake located in said brake space and at least in part in said gapproximate to and between said pair of bearings.
 2. A device according toclaim 1 wherein said rotor includes a rotor part and a stator part.
 3. Adevice according to claim 2 wherein the rotor part is clamped between ashoulder formed on an inner face of the rim well and a pressure ring. 4.A device according to claim 3 wherein a seal is arranged between thepressure ring and the inner housing ring.
 5. A device according to claim1 wherein the brake includes a plurality of brake discs projecting intothe brake space between a plurality of brake rings.
 6. A deviceaccording to claim 5 wherein each of the plurality of brake discs isseated on the axle shaft and is displaceable along the axis A of theaxle shaft.
 7. A device according to claim 6 wherein each of saidplurality of brake discs is mounted on the axle shaft by means of asplined connection.
 8. A device according to claim 7 wherein each ofsaid plurality of brake rings is mounted on the inner housing ring bymeans of a splined connection.
 9. A device according to claim 5 whereineach of said plurality of brake rings is mounted on the inner housingring by means of a splined connection.
 10. A device according to claim 9wherein the brake rings include an outer brake ring and a spring acts onthe outer brake ring for moving the brake rings along the axis A of theaxle shaft.
 11. A device according to claim 10 wherein the outer brakering is actuated by a magnetic coil.
 12. A device according to claim 11wherein the magnetic coil is located in an annular space defined by aferrite ring between the inner housing ring and the axle shaft.
 13. Adevice according to claim 10 wherein the outer brake ring is connectedto a device for manually actuating the brake.
 14. A drive device for anelectrically operated vehicle comprises an axle shaft disposed along anaxis A; at least one rim connected to the axle shaft for rotationtherewith, said at least one rim having a rim well wherein said rim welland said axle shaft define therebetween an annular channel; an innerhousing ring positioned in said annular channel disposed among an axis Bwhich is substantially parallel to axis A and axially dividing saidannular channel into a motor space and a brake space, said inner housingring being supported on the axle shaft by a pair of bearings axiallydisplaced on the axle shaft along axis A and defining therebetween insaid brake space a gap; and a brake located in said brake space and atleast in part in said gap proximate to said pair of bearings whereinsaid brake comprises a plurality of brake rings and a plurality of brakediscs alternately located within said brake space.
 15. A deviceaccording to claim 14 wherein said motor includes a rotor part and astator part.
 16. A device according to claim 15 wherein the rotor partis clamped between a shoulder formed on an inner face of the rim welland a pressure ring.
 17. A device according to claim 16 wherein a sealis arranged between the pressure ring and the inner housing ring.
 18. Adevice according to claim 14 wherein the brake includes a plurality ofbrake discs projecting into the brake space between a plurality of brakerings.
 19. A device according to claim 18 wherein each of the pluralityof brake discs is seated on the axle shaft and is displaceable along theaxis A of the axle shaft.
 20. A device according to claim 19 whereineach of said plurality of brake discs is mounted on the axle shaft bymeans of a splined connection.
 21. A device according to claim 20wherein each of said plurality of brake rings is mounted on the innerhousing ring by means of a splined connection.
 22. A device according toclaim 18 wherein each of said plurality of brake rings is mounted on theinner housing ring by means of a splined connection.
 23. A deviceaccording to claim 22 wherein the brake rings include an outer brakering and a spring acts on the outer brake ring for moving the brakerings along the axis A of the axle shaft.
 24. A device according toclaim 23 wherein the outer brake ring is actuated by a magnetic coil.25. A device according to claim 24 wherein the magnetic coil is locatedin an annular space defined by a ferrite ring between the inner housingring and the axle shaft.
 26. A device according to claim 23 wherein theouter brake ring is connected to a device for manually actuating thebrake.